1. Field
The following description relates to a rotated quadrature amplitude modulation (QAM) based communication system, and more particularly, to a method and an apparatus to perform a soft demapping on a received symbol in a rotated QAM based communication system.
2. Description of Related Art
A wireless communication system and a broadcasting system may use a rotated quadrature amplitude modulation (QAM) transmission technology. For example, a digital video broadcasting (DVB) standard, for example, a digital video broadcasting-second generation terrestrial (DVB-T2) standard, prescribes that data be transmitted based on the rotated QAM.
Fading may occur in a wireless channel of a wireless communication system. Here, the fading refers to attenuation of a wireless signal during transmission of the wireless signal. To combat fading problems, a diversity method may be employed, which includes spatial diversity and frequency diversity. A signal-space diversity method is being adopted by a great number of technologies, including the DVB-T2 standard, to address fading problems. As an example, a rotated QAM constellation may be used to implement the signal-space diversity method. However, when a transmitter uses the rotated QAM, a receiver would have to execute a complex process to perform a soft demapping.